Question

我正在尝试找到一种方法，在为第一个主键列添加新条目时自动增加表中的第二个主键列。我想这里的例子最好，所以这里就是。

假设我有一张桌子：

CREATE TABLE T
(
     SecNum INT NOT NULL,
     EntryID INT NOT NULL,
     Value FLOAT,
) CONSTRAINT [PK_T] PRIMARY KEY CLUSTERED 
(
    [SecNum] ASC,
    [EntryID] ASC
)

我会运行以下声明：

INSERT INTO T (SecNum, Value) VALUES (0, 10)

我的表应该如下：

SECNUM | ENTRYID | VALUE
-------------------------
   0         0       10

我会运行以下声明：

INSERT INTO T (SecNum, Value) VALUES (0, 10)

我的表应该如下：

SECNUM | ENTRYID | VALUE
-------------------------
   0         0       10
   0         1       10

我会运行以下声明：

INSERT INTO T (SecNum, Value) VALUES (1, 20)

我的表应该如下：

SECNUM | ENTRYID | VALUE
-------------------------
   0         0       10
   0         1       10
   1         0       20

Answer 1

使用INSTEAD OF触发器可以实现这一点：

CREATE TRIGGER TriggerName
ON T
INSTEAD OF INSERT
AS
    -- THIS TOP BIT IS OPTIONAL, IT WILL ALLOW ENTRY ID TO BE OVERRIDDEN IF 
    -- IT IS SUPPLIED TO THE INSERT AND WILL NOT VIOLATE THE PRIMARY KEY
    IF NOT EXISTS 
        (   SELECT  1
            FROM    T
                    INNER JOIN inserted i
                        ON i.SecNum = T.secNum
                        AND i.EntryID = T.EntryID
            UNION
            SELECT  1
            FROM    inserted
            WHERE   EntryID IS NULL
        )
        BEGIN
            INSERT T (SecNum, EntryID, Value)
            SELECT  SecNum, EntryID, Value
            FROM    inserted
        END
    ELSE
    -- IF OVERRIDE ABILITY IS NOT REQUIRED JUST USE THE BELOW INSERT
        BEGIN
            INSERT T (SecNum, EntryID, Value)
            SELECT  i.SecNum, COALESCE(LastID, 0), i.Value
            FROM    inserted I
                    LEFT JOIN 
                    (   SELECT  SecNum, MAX(T.EntryID) + 1 [LastID]
                        FROM    T
                        GROUP BY SecNum
                    ) T
                        ON T.SecNum = i.SecNum

        END

Example here

HOWEVER 这不是很优雅。值得一提的是它真的有必要吗？您是否可以使用代理主键，并使用ROW_NUMBER()动态创建条目ID？

Answer 2

使用instead of insert触发器

可以解决您的问题

 create trigger Trigger1 on T INSTEAD OF INSERT
 as
 begin                                  
       insert into T(SecNum,EntryID,Value)
       select SecNum,
             (select count(*) from T where SecNum = i.SecNum) as EntryID, 
             value 
       from inserted i
 end

Answer 3

这样的事情怎么样：

INSERT INTO T (SecNum, Value, EntryId)
SELECT 0, 10, count(*)
FROM T WHERE SecNum = 0

这不是最干净的解决方案，也会表现得非常糟糕。但它应该完成工作。

Answer 4

这是如何在不将值存储在表中的情况下完成的（我不知道你为什么要存储它）

表格

DECLARE @T TABLE ( SecNum INT NOT NULL, EntryID INT, Value FLOAT )

数据

INSERT INTO @T ( SecNum, Value ) VALUES ( 0, 10 ) INSERT INTO @T ( SecNum, Value ) VALUES ( 0, 10 ) INSERT INTO @T ( SecNum, Value ) VALUES ( 1, 20 )

<强> QUERY

SELECT SecNum, ROW_NUMBER() OVER ( PARTITION BY value ORDER BY Value ) - 1 AS EntryID, Value FROM @T

<强> RESULT

SecNum EntryID Value 0 0 10 0 1 10 1 0 20

如果EntryID随SecNum AND Value更改，请使用此查询：

SELECT SecNum, ROW_NUMBER() OVER ( PARTITION BY Value,SecNum ORDER BY Value, SecNum ) - 1 AS EntryID, Value FROM @t

结果2

SecNum EntryID Value 0 0 10 0 1 10 1 0 10 1 0 20

如何为第一个主键列添加新条目时，如何自动增加表中的第二个主键列

4 个答案: